A mechanical lubricant vane pump, as described in WO 2011/107156 A1, is generally a volumetric pump which is mechanically driven by an engine so that the pump rotates with a rotational speed which is proportional to the engine's rotational speed. The lubricant vane pump is provided with a pump rotor body holding radially slidable vanes rotating inside a shiftable control ring. The slidable vanes, the rotor body, and the control ring wall define a plurality of rotating pump compartments which rotate within a pump chamber to thereby pump the lubricant from an inlet cavity to an outlet cavity of the pump.
The control ring is shiftable with respect to the rotor axis between a high pumping volume position with high eccentricity, and a low pumping volume position with low eccentricity, so that the lubricant volume per rotation pumped by the pump can be adapted to keep the discharge pressure of the pump at a constant level. The eccentricity position of the control ring with respect to the rotational axis of the pump rotor is determined by two counter acting hydraulic chambers, i.e., the pressure control chamber for pushing the control ring into a high pumping volume direction and the pilot chamber for pushing the control ring into a low pumping volume direction against the pressure control chamber. Both chambers are fluidically connected to the outlet cavity by respective fluidic channels.
The pilot chamber is connected to the outlet cavity by a pilot chamber channel with a large cross-section so that the fluidic resistance is low. The control chamber is connected to the outlet cavity by a relatively long control chamber channel with a pressure throttle valve in the course of the control chamber channel. The fluidic pressure in the control chamber is controlled by a control valve which allows the pressure control chamber to be connected or disconnected to a lubricant tank which is under atmospheric pressure. The control valve itself is controlled by the discharge pressure of the pump or by the effective lubricant pressure in or at the engine.
After a cold start of the engine, the pilot chamber of the pump is filled relatively quickly with the cold and viscous lubricant because the fluidic resistance between the outlet cavity and the pilot chamber is relatively low. The control ring is thereby pushed into the low pumping volume direction right after the engine's cold start. In contrast to the pilot chamber, it takes a while until the control chamber is filled with lubricant and is pressurized with the fluidic pressure of the outlet cavity because the fluidic resistance between the outlet cavity and the control chamber is relatively high due to the long control chamber channel and the throttle provided in the course of the control chamber channel. It can therefore take 5, 10 or even more than 60 seconds after an engine's cold start until pressurized lubricant is generated by the pump and until the engine is sufficiently lubricated after a cold start of the engine.
In addition to the fact that the engine runs at a high mechanical resistance without sufficient lubrication, the wear of the engine and the danger of jamming are high with non-sufficient lubrication.